Deployment Guide

• Inter-switch stacking link failure
• Switch insertion
• Switch removal
If the master switch goes o line, the standby replaces it as the new master.
NOTE: For the Aggregator, the entire stack has only one management IP address.
Stack Master Election
The stack elects a master and standby unit at bootup time based on MAC address. The unit with the higher MAC value becomes master.
To view which switch is the stack master, enter the show system command. The following example shows sample output from an
established stack.
A change in the stack master occurs when:
• You power down the stack master or bring the master switch oine.
• A failover of the master switch occurs.
• You disconnect the master switch from the stack.
NOTE: When a stack reloads and all the units come up at the same time; for example, when all units boot up from ash, all units
participate in the election and the master and standby are chosen based on the priority on the MAC address. When the units do
not boot up at the same time, such as when some units are powered down just after reloading and powered up later to join the
stack, they do not participate in the election process, even though the units that boot up late may have a higher priority
congured. This happens because the master and standby have already been elected, hence the unit that boots up late joins only
as a member. Also, when an up and running standalone unit or stack is merged with another stack, based on election, the losing
stack reloads and the master unit of the winning stack becomes the master of the merged stack. To ensure a fully synchronised
bootup, it is possible to reset individual units to force them to give up the management role; or reload the whole stack from the
command line interface (CLI).
Example of Viewing Stack Members
Dell# show system brief
Stack MAC : 00:1e:c9:f1:00:9b
-- Stack Info --
Unit UnitType Status ReqTyp CurTyp Version Ports
------------------------------------------------------------------------------------
0 Management online I/O-Aggregator I/O-Aggregator 8-3-17-46 56
1 Standby online I/O-Aggregator I/O-Aggregator 8-3-17-46 56
2 Member not present
3 Member not present
4 Member not present
5 Member not present
Dell#
Failover Roles
If the stack master fails (for example, powered o), it is removed from the stack topology. The standby unit detects the loss of peering
communication and takes ownership of the stack management, switching from standby to master. The lack of a standby unit triggers an
election within the remaining units for a standby role.
After the former master switch recovers, despite having a higher priority or MAC address, it does not recover its master role but instead
takes the next available role.
Stacking
243